Conventional touch sensing devices have typically been capacitive and resistance based. These types of touch sensing devices may be desirable because many stylists have proclivities toward designs with continuity, or continuous surfaces in general. For example, automotive stylists appear to be moving toward sleek, continuous instrument panels and center consoles. Stylists and consumers may prefer a smooth, continuous touch screen to control the functions of their automobiles, instead of mechanical dials and push buttons. Capacitive and resistance based touch sensing devices make this style choice a reality. Capacitive and resistance based touch sensing devices may also be beneficial because their switch packages are generally smaller and lighter than mechanical-type switch packages.
Despite the advantages of capacitive and resistance based touch sensing devices, there remains drawbacks. For example, capacitive touch sensing devices may not work well when condensation is present on the touch sensing surface, and may be inoperable when an operator is wearing gloves. Capacitive based touch sensing devices generally rely on an electrically conducting stylus; thus, capacitive based touch sensing devices may fail to perform as intended in these circumstances. Further, a stylist is limited to materials that can be used for capacitive and resistance based touch sensing devices.
Optical touch sensing devices address at least some of the challenges of capacitive and resistance based touch sensing devices. However, optical based touch sensing devices may face different issues. For example, an operator may inadvertently actuate an optical touch sensing device, which in some circumstances may place the operator in danger.
Thus, there is a need for an optical sensing device that avoids inadvertent actuation.